4), which were identical to the aforementioned products in culture supernatants of the transposon mutant strain G12. Notably, in contrast

to strain G12, strain Chol1-KO[skt] performed this conversion without prior induction through growth with DHADD. The reason for this difference between strains G12 and Chol1-KO[skt] is not known. Among the accumulating products, one peak, P1, was dominant (Fig. 4). This compound had a second UV-absorption maximum around 210 nm in addition to the maximum at 244 nm. A further compound with Selleck ABT 888 a UV-absorption maximum at 244 nm eluted very close to P1, thereby causing a shoulder tailing off from the P1 peak. As a better separation of these two compounds could not be achieved, it is likely that they have a very similar structure. A relatively small peak, P2, eluted several minutes earlier than all other products.

This compound occurred in low amounts and was relatively unstable. Compounds P1 and P2 were purified and analyzed by NMR and MS. As sample P1 contained a slight amount of impurities from the compound eluting very close to it and as sample P2 had a relatively low concentration, the de novo chemical shift assignment was difficult. However, the NMR spectra of both compounds showed high similarities in their Δ1,4-3-ketocholate framework such that the assignment of the four steroid rings was facilitated by comparison with the chemical shift assignment of DHOPDC (Birkenmaier et Selleckchem Obeticholic Acid al., 2007) (Table 1). Compound P1 contains an additional unsaturation, whereas compound P2 contains Anidulafungin (LY303366) an additional hydroxyl group. Both modifications do not affect the pattern of chemical shifts of the four steroid rings. The attachment of the hydroxyl group of P2 at C22 could be identified from the characteristic HSQC crosspeak at 4.09/70.5 p.p.m. and correlations, from COSY, TOCSY and HMBC, into the side chain and ring D. Compound P1 exhibits an additional C–C double bond with chemical shifts of 5.82/118.3 p.p.m. and 6.93/157.4 p.p.m., respectively. The location of this olefinic group could be established again from its correlations within the side chain and to the D-ring. According

to the scalar coupling of 15 Hz between the olefinic protons, the double bond has an E-configuration. The absolute configuration at C20 (P1, P2) and C22 (P2) could not be determined because of insufficient amount of sample. The stereospecific assignments at C6, C7, C11, C12, C15 and C16 were carried out according to their similarity of chemical shifts as compared with DHOPDC (Birkenmaier et al., 2007). According to these NMR-spectroscopic data, P1 was identified as (22E)-7α,12α-dihydroxy-3-oxochola-1,4,22-triene-24-oate (DHOCTO, XI) and P2 was identified as 7α,12α,22-trihydroxy-3-oxochola-1,4-diene-24-oate (THOCDO, XII). Analysis by LC–MS revealed ions [M+H]+ with m/z 401.23 and m/z 419.24 for P1 and P2, respectively.